A Class for Creating a Trace Log

So the Debug build works great, but the Release build crashes? Or the program works fine on your computer, but crashes on the customer's computers? You need to add trace functionality to the Release build.

CLogTrace is a class that allows you to easily add trace functionality to the release build of a program. You make the program write lines of text to a log file at various stages in the program. You provide the code to turn the logging on or off. Much like using the TRACE macro, you get a text file that tells you what functions were called, with a date/time stamp. Except you can get this information in release builds.

The class is easy to use.

Make a static CLogTrace object as a member of the application class

Add the initialization lines in the programs InitInstance function.

Any time you want to write to the log file, use the CLogTrace::WriteLine functions
these will write the text along with date and time

////////////////////////////////////////////////////////////////////////
// LogTrace.cpp -- Implementation of the CLogTrace class
#include "stdafx.h"
#include "LogTrace.h"/**************************************************
How to use CLogTrace
1. Make a static CLogTrace object as a member of the application class
2. Add the following lines to the InitInstance of the program
m_LogTrace.m_strAppName = "MyApp"; // use appropriate name here
m_LogTrace.SetFileName("Log.txt"); // sets the log file name and puts it in the exe path
m_LogTrace.OnStartup(TRUE, TRUE); // activates the log trace
3. Also in InitInstance, add the following line if you want to empty the log file
each time the application starts
m_LogTrace.ResetFile();
4. Any time you want to write to the log file, use the CLogTrace::WriteLine functions
these will write the text along with date and time
*******************************************************///////////////////////////////////////////////////////
// Construction/Destruction
CLogTrace::CLogTrace()
{
m_bActive = FALSE;
m_bTimeStamp = TRUE;
CString s;
}
CLogTrace::~CLogTrace()
{
}
////////////////////////////////////////////////////////
// CLogTrace operationsvoid CLogTrace::ResetFile()
{
CStdioFile f;
CFileException fe;
CString s;
if (m_strFileName.IsEmpty()) return;
if (f.Open(m_strFileName, CFile::modeWrite | CFile::modeCreate, &fe) == FALSE)
{
return;
}
f.Close();
}
// bActive tells us if we want the trace to be active or not// bTimeStamp tells us if we want time stamps on each line// eliminating the time stamp allows us to use this class for a regular log filevoid CLogTrace::OnStartup(BOOL bActive, BOOL bTimeStamp)
{
m_bActive = bActive;
m_bTimeStamp = bTimeStamp;
if (bTimeStamp == FALSE) return;
CString s;
// these ***'s help to indicate when one ru of the program ends and another starts// because we don't always overwrite the file each time
WriteLine("\n\n******************************************\n\n");
s.Format("%s Log Trace %s\n\n", m_strAppName, COleDateTime::GetCurrentTime().Format());
WriteLine(s);
}
// function to write a line of text to the log filevoid CLogTrace::WriteLine(LPCTSTR szLine)
{
CStdioFile f;
CFileException fe;
CString s;
if (m_bActive == FALSE) return;
if (m_strFileName.IsEmpty()) return;
if (f.Open(m_strFileName, CFile::modeWrite | CFile::modeCreate |
CFile::modeNoTruncate, &fe) == FALSE)
{
return;
}
try
{
f.SeekToEnd();
TRACE("LOGGIN %s\n", szLine);
if (m_bTimeStamp)
{
s.Format("%s\t%s\n", COleDateTime::GetCurrentTime().Format(),
szLine);
}
else
{
s.Format("%s\n", szLine);
}
f.WriteString(s);
}
catch (CException* e)
{
// Note that there is not much we can do if there is an exception// It is not practical to tell the user each time// and we can't write the error to a log file!!!!
e->Delete();
}
f.Close();
}
// function to write a line of text, with an extra stringvoid CLogTrace::WriteLine(LPCTSTR szFormat, LPCTSTR szAddInfo)
{
if (m_bActive == FALSE) return;
CString s;
s.Format(szFormat, szAddInfo);
WriteLine(s);
}
// funtion to write a line of text with an extra integervoid CLogTrace::WriteLine(LPCTSTR szFormat, int nAddInfo)
{
if (m_bActive == FALSE) return;
CString s;
s.Format(szFormat, nAddInfo);
WriteLine(s);
}
// function to set the log file name. don't pass a fill path!// just pass something like "log.txt"// the file will be placed in the same dir as the exe filevoid CLogTrace::SetFileName(LPCTSTR szFileName)
{
TCHAR drive[_MAX_PATH], dir[_MAX_PATH], name[_MAX_PATH], ext[_MAX_PATH];
constchar *path = _pgmptr ;
_splitpath(path, drive, dir, name, ext);
m_strFileName.Format("%s%s%s", drive, dir, szFileName);
}

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About the Author

Bob Pittenger is founder and President of Starpoint Software Inc. He holds a B.A. degree from Miami University, M.S. and Ph.D. degrees from Purdue University, and an MBA from Xavier University. He has been programming since 1993, starting with Windows application development in C++/MFC and moving to C# and .NET around 2005 and is a .NET Microsoft Certified Professional Developer.

Bob is the author of two books:
Billionaire: How the Ultra-Rich Built Their Fortunes Through Good and Evil and What You Can Learn from Them
and
Wealthonomics: The Most Important Economic and Financial Concepts that Can Make You Rich Fast.
Visit http://www.billionairebook.net for more information.